Conventional wisdom dictates that the more money a country's citizens have, the more they'll travel. It's an assumption broadly borne out by data, but it's especially appealing due to the parallels between macro-level trends and personal experience: In the same way a richer society will demand more travel resources, cars and air travel are closely associated with personal wealth.

This is a safe assumption when applied to the developing world, for which the developed world supplies plenty of data about the correlation between GDP and travel. But researchers at Berkeley and Stanford Universities claim to have found a point at which this correlation breaks down. Our appetite for travel, it seems, has its limits. To put it more dramatically, the developed world appears to have reached "Peak Travel."

The report charts the relationship between countries' wealth (using GDP as an indicator) and travel habits, using data collected from the United States, Canada, Sweden, France, Germany, the United Kingdom, Japan and Australia from 1970-2008. A few of its salient findings:

For the first 30 years, growth in miles traveled and car ownership were fairly steady. It wasn't until the year 2000 that passenger travel seemed to level out

In the US, passenger travel peaked when the GDP per capita hit $37,000; in most other countries, this peak arrived between $25,000 and $30,000

US car travel peaked at 8,100 miles per person per year, the highest of the group by far. All, however, have held steady or declined in the last 10 years

Car ownership is stagnant

Cars have on average become more efficient, using less fuel per mile than they did 20 years ago

So, what has stalled passenger travel in the developed world? The paper point to congestion, gas prices, fear of increasing gas prices, parking problems, and a decrease in commuting--though mainly as a result of a proportional increase in non-working old citizens.

Perhaps the most intuitive take, though, comes from the paper's co-author, Lee Schipper, who tells Miller McCune, "You get to a point where everybody who could possibly drive, drives."

The existence of "Peak Travel" has massive economic implications, and will--and has already begun to--steer the global auto industry away from its dependence on indefinite growth, at least in the United States, Western Europe and Japan.

It also has potentially huge implications for the environment, just not for a while. As the paper's authors point out, any stabilization or decrease in greenhouse gas emissions in the developed world will surely be overwhelmed by the growth in travel in countries like China and India, each with populations exceeding 1bn and plenty of expected economic growth in store over the next few decades.

What's more interesting is how these findings can be applied to nations where travel is still on the rise. Thedata doesn't just highlight the possibility of an eventual Global Peak Travel scenario--it provides some guidance for predicting plateaus on a country by country basis.